Chevrolet Cobalt Service & Repair Manual: System Inspection
| The individual components of the
refrigerant system will often give clear signs of their malfunctioning.
Use the following general descriptions to pinpoint faulty components. |
| While a detailed diagnostic procedure
for all air conditioning systems would be impractical due to the many variations
in construction and operation, there are three fundamental components of
a total diagnosis: |
| 1. |
Refrigerant systems must have an adequate,
but not excessive charge. |
| 2. |
Determination must be made whether
the refrigerant system is governed by a cycling clutch compressor
or by valves which control evaporator pressure. |
| 3. |
The air distribution system (blower
motor, switches, vacuum lines and air ducts) must be operational
before checking the refrigerant system. |
|
| Check the blower; if inoperative,
examine switches, fuses, connections, wiring and the blower motor. If blower
is operating but the air output is low, check for loose wire connections
or shorts, undercharged battery, dirty or loose switch contacts, or a faulty
blower motor. Inspect the air distribution system for obstructions and ensure
proper door operation. |
| If the blower is circulating the
air but there is no cooling, check the compressor drive belt; ensure it
is not broken or slipping. If the pulley is turning but the compressor shaft
is not, check the magnetic clutch. On models equipped with a cycling clutch,
the following hand check method will determine whether the problem lies
in the refrigerant system or further testing of the distribution system
is required. |
| 1. |
With engine warmed up and at normal
idle, set selector lever to Norm, temperature lever to Cold and
blower on Hi. |
| 2. |
Place one hand on the evaporator inlet
pipe and the other on the receiver/drier surface with the compressor
engaged. |
| 3. |
If both surfaces are the same temperature
and colder than ambient temperature, refrigerant system is normal. |
| 4. |
If the inlet pipe is cooler than the
receiver/drier surface, refrigerant system is low on charge. Add
small amounts of refrigerant until both feel the same temperature.
Then add 14 oz. (one can) of additional refrigerant. |
| 5. |
If inlet pipe is frosted over and receiver/drier
surface is warmer, proceed as in step 4. |
|
Compressor
| A faulty compressor will display
one or more of the following symptoms: noise, seizure, leakage or low inlet
and discharge pressure. A steady, resonant noise from the compressor is
not necessarily an indication of a problem, but irregular metallic rattling
may indicate broken parts and should be investigated. A thumping noise from
the compressor and a cool, sweating suction line into it may indicate an
overcharged system. Check seizure by disengaging the magnetic clutch and
rotating the driven plate. If the compressor is seized, the driven plate
will not rotate. |
| False compressor seizure may occur
after an extended period of disuse or storage. Lubricating oil drains away
from the polished surfaces of ball seats and axial plate and the compressor
appears to be seized. Use a clutch hub holding tool to turn the compressor
in the opposite direction of rotation at least three revolutions. Check
for false compressor seizure if compressor has not been used in a month
or longer. |
| If compressor is not seized but
will not rotate, check for current at magnetic coil. Low discharge pressure
may be caused by faulty seals within the compressor, a restriction in the
compressor or elsewhere, or by a low refrigerant charge. The compressor
must have the correct amount of the proper viscosity oil. Excess oil will
restrict refrigerant circulation and reduce compressor outlet pressure. |
Condenser
| The condenser may malfunction
either due to leakage or restriction. If restricted, compressor discharge
pressure will be excessive. Icy or frosty spots on the condenser will indicate
a partial restriction within the condenser. Ensure all foreign matter is
removed from the front of the condenser. Similarly, bent cooling fins will
block air flow through the condenser and result in high discharge pressures. |
Evaporator
| A faulty evaporator will provide
insufficient cooling to the vehicle. The core may be restricted with dirt,
the case may be cracked, or a seal may be leaking sufficiently to prevent
cooling. If evaporator restriction is due to icing, the expansion valve,
capillary tube or suction throttling valve, if equipped, may be at fault
and should be investigated. |
| Since there is a constant condensation
of atmospheric moisture on the outside of the evaporator coils, ensure the
draining system is unobstructed and clean. Some vehicles have an auxiliary
evaporator in the trunk or between the headliner and the roof. |
Receiver-Dryer/Accumulator
| A restriction inside the receiver-dehydrator/accumulator
will result in high head pressures if the restriction is on the inlet side
of the unit. A restriction at the outlet side will cause low head pressures
and little or no cooling. An exceedingly cold receiver-dehydrator/accumulator
may be restricted. |
| If the system has been in service
for a considerable amount of time, the desiccant element may have lost its
moisture absorbing ability. This condition is indicated by the constant
presence of small bubbles in the sight glass if equipped and a wide difference
in temperature between the inlet and outlet receiver-dehydrator/accumulator
lines. |
Thermostatic Expansion Valve
| Faulty expansion valves will be
indicated by low suction and discharge pressures on the manifold gauge set.
In most cases the power element fails and the valve closes. Occasionally
the inlet screen becomes clogged with contamination or desiccant beads are
loose in the system. |
Refrigerant Line Restrictions
| 1. |
A restricted suction line is indicated
by low suction pressure at the compressor, low discharge pressure
and little or no cooling. |
| 2. |
A restricted discharge line will usually
cause the pressure relief valve to open. |
| 3. |
A restricted liquid line will cause
low suction and discharge pressures and little or no cooling. |
|
The refrigerant system must be
discharged using an air conditioning refrigerant recovery and recycling
system. After completing any required repairs the refrigerant system can
be ev ...
Chevrolet Cobalt Owners Manual
Chevrolet Cobalt Service Manual
Refrigerant Recovery
Body & Frame